default to the one defined in price_parameter_dict. As mapped_value is a
TempSupplyCell, we don't want to retrieve default valued from one of
SupplyCell's property sheet properties.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@19848 20353a03-c40f-0410-a6d1-a30d3c3de9de